| Message ID | 20240805152004.5039-7-dakr@kernel.org (mailing list archive) |
|---|---|
| State | New |
| Headers | show |
| Series | Generic `Allocator` support for Rust | expand |
On 05.08.24 17:19, Danilo Krummrich wrote: > Implement `Allocator` for `Vmalloc`, the kernel's virtually contiguous > allocator, typically used for larger objects, (much) larger than page > size. > > All memory allocations made with `Vmalloc` end up in `vrealloc()`. > > Reviewed-by: Alice Ryhl <aliceryhl@google.com> > Signed-off-by: Danilo Krummrich <dakr@kernel.org> > --- > rust/helpers.c | 7 +++++++ > rust/kernel/alloc/allocator.rs | 32 +++++++++++++++++++++++++++++ > rust/kernel/alloc/allocator_test.rs | 1 + > 3 files changed, 40 insertions(+) > > diff --git a/rust/helpers.c b/rust/helpers.c > index 9f7275493365..7406943f887d 100644 > --- a/rust/helpers.c > +++ b/rust/helpers.c > @@ -33,6 +33,7 @@ > #include <linux/sched/signal.h> > #include <linux/slab.h> > #include <linux/spinlock.h> > +#include <linux/vmalloc.h> > #include <linux/wait.h> > #include <linux/workqueue.h> > > @@ -199,6 +200,12 @@ void *rust_helper_krealloc(const void *objp, size_t new_size, gfp_t flags) > } > EXPORT_SYMBOL_GPL(rust_helper_krealloc); > > +void *rust_helper_vrealloc(const void *p, size_t size, gfp_t flags) > +{ > + return vrealloc(p, size, flags); > +} > +EXPORT_SYMBOL_GPL(rust_helper_vrealloc); > + > /* > * `bindgen` binds the C `size_t` type as the Rust `usize` type, so we can > * use it in contexts where Rust expects a `usize` like slice (array) indices. > diff --git a/rust/kernel/alloc/allocator.rs b/rust/kernel/alloc/allocator.rs > index c6ad1dd59dd0..bb55895cbd03 100644 > --- a/rust/kernel/alloc/allocator.rs > +++ b/rust/kernel/alloc/allocator.rs > @@ -9,6 +9,7 @@ > > use crate::alloc::{AllocError, Allocator}; > use crate::bindings; > +use crate::pr_warn; > > /// The contiguous kernel allocator. > /// > @@ -16,6 +17,12 @@ > /// `bindings::krealloc`. > pub struct Kmalloc; > > +/// The virtually contiguous kernel allocator. > +/// > +/// The vmalloc allocator allocates pages from the page level allocator and maps them into the > +/// contiguous kernel virtual space. > +pub struct Vmalloc; One thing that I should also have mentioned for `Kmalloc`, do we want these types to also have values? I don't think that we need them to be, so we could declare them as `pub enum Vmalloc {}`. > + > /// Returns a proper size to alloc a new object aligned to `new_layout`'s alignment. > fn aligned_size(new_layout: Layout) -> usize { > // Customized layouts from `Layout::from_size_align()` can have size < align, so pad first. > @@ -61,6 +68,11 @@ fn krealloc() -> Self { > Self(bindings::krealloc) > } > > + // INVARIANT: `vrealloc` satisfies the type invariants. This should be moved down a line. --- Cheers, Benno > + fn vrealloc() -> Self { > + Self(bindings::vrealloc) > + } > + > /// # Safety > /// > /// This method has the exact same safety requirements as `Allocator::realloc`. > @@ -141,6 +153,26 @@ unsafe fn alloc_zeroed(&self, layout: Layout) -> *mut u8 { > } > } > > +unsafe impl Allocator for Vmalloc { > + unsafe fn realloc( > + ptr: Option<NonNull<u8>>, > + layout: Layout, > + flags: Flags, > + ) -> Result<NonNull<[u8]>, AllocError> { > + let realloc = ReallocFunc::vrealloc(); > + > + // TODO: Support alignments larger than PAGE_SIZE. > + if layout.align() > bindings::PAGE_SIZE { > + pr_warn!("Vmalloc does not support alignments larger than PAGE_SIZE yet.\n"); > + return Err(AllocError); > + } > + > + // SAFETY: If not `None`, `ptr` is guaranteed to point to valid memory, which was previously > + // allocated with this `Allocator`. > + unsafe { realloc.call(ptr, layout, flags) } I am a bit confused, for `Kmalloc`, you manually returned `NonNull::dangling` when allocating a zero-sized allocation, but here you don't? --- Cheers, Benno > + } > +} > + > #[global_allocator] > static ALLOCATOR: Kmalloc = Kmalloc; > > diff --git a/rust/kernel/alloc/allocator_test.rs b/rust/kernel/alloc/allocator_test.rs > index 4785efc474a7..e7bf2982f68f 100644 > --- a/rust/kernel/alloc/allocator_test.rs > +++ b/rust/kernel/alloc/allocator_test.rs > @@ -7,6 +7,7 @@ > use core::ptr::NonNull; > > pub struct Kmalloc; > +pub type Vmalloc = Kmalloc; > > unsafe impl Allocator for Kmalloc { > unsafe fn realloc( > -- > 2.45.2 >
diff --git a/rust/helpers.c b/rust/helpers.c index 9f7275493365..7406943f887d 100644 --- a/rust/helpers.c +++ b/rust/helpers.c @@ -33,6 +33,7 @@ #include <linux/sched/signal.h> #include <linux/slab.h> #include <linux/spinlock.h> +#include <linux/vmalloc.h> #include <linux/wait.h> #include <linux/workqueue.h> @@ -199,6 +200,12 @@ void *rust_helper_krealloc(const void *objp, size_t new_size, gfp_t flags) } EXPORT_SYMBOL_GPL(rust_helper_krealloc); +void *rust_helper_vrealloc(const void *p, size_t size, gfp_t flags) +{ + return vrealloc(p, size, flags); +} +EXPORT_SYMBOL_GPL(rust_helper_vrealloc); + /* * `bindgen` binds the C `size_t` type as the Rust `usize` type, so we can * use it in contexts where Rust expects a `usize` like slice (array) indices. diff --git a/rust/kernel/alloc/allocator.rs b/rust/kernel/alloc/allocator.rs index c6ad1dd59dd0..bb55895cbd03 100644 --- a/rust/kernel/alloc/allocator.rs +++ b/rust/kernel/alloc/allocator.rs @@ -9,6 +9,7 @@ use crate::alloc::{AllocError, Allocator}; use crate::bindings; +use crate::pr_warn; /// The contiguous kernel allocator. /// @@ -16,6 +17,12 @@ /// `bindings::krealloc`. pub struct Kmalloc; +/// The virtually contiguous kernel allocator. +/// +/// The vmalloc allocator allocates pages from the page level allocator and maps them into the +/// contiguous kernel virtual space. +pub struct Vmalloc; + /// Returns a proper size to alloc a new object aligned to `new_layout`'s alignment. fn aligned_size(new_layout: Layout) -> usize { // Customized layouts from `Layout::from_size_align()` can have size < align, so pad first. @@ -61,6 +68,11 @@ fn krealloc() -> Self { Self(bindings::krealloc) } + // INVARIANT: `vrealloc` satisfies the type invariants. + fn vrealloc() -> Self { + Self(bindings::vrealloc) + } + /// # Safety /// /// This method has the exact same safety requirements as `Allocator::realloc`. @@ -141,6 +153,26 @@ unsafe fn alloc_zeroed(&self, layout: Layout) -> *mut u8 { } } +unsafe impl Allocator for Vmalloc { + unsafe fn realloc( + ptr: Option<NonNull<u8>>, + layout: Layout, + flags: Flags, + ) -> Result<NonNull<[u8]>, AllocError> { + let realloc = ReallocFunc::vrealloc(); + + // TODO: Support alignments larger than PAGE_SIZE. + if layout.align() > bindings::PAGE_SIZE { + pr_warn!("Vmalloc does not support alignments larger than PAGE_SIZE yet.\n"); + return Err(AllocError); + } + + // SAFETY: If not `None`, `ptr` is guaranteed to point to valid memory, which was previously + // allocated with this `Allocator`. + unsafe { realloc.call(ptr, layout, flags) } + } +} + #[global_allocator] static ALLOCATOR: Kmalloc = Kmalloc; diff --git a/rust/kernel/alloc/allocator_test.rs b/rust/kernel/alloc/allocator_test.rs index 4785efc474a7..e7bf2982f68f 100644 --- a/rust/kernel/alloc/allocator_test.rs +++ b/rust/kernel/alloc/allocator_test.rs @@ -7,6 +7,7 @@ use core::ptr::NonNull; pub struct Kmalloc; +pub type Vmalloc = Kmalloc; unsafe impl Allocator for Kmalloc { unsafe fn realloc(